Disposable cups for holding hot beverages may be constructed of expanded polystyrene which provides a cup of relatively low cost with walls having good thermal insulation. The insulating properties of the outer walls of the cup allow the cup to be comfortably held despite the high temperature of its contents. A disadvantage with polystyrene is that it is neither biodegradable, readily recycled nor microwavable.
In contrast, paper cups are both recyclable and biodegradable but such cups, using a single sheet of paper for their outer walls, provide little thermal insulation. It has therefore been proposed to construct the outer wall of a paper cup of multi-ply corrugated paper material, the air trapped between the flutes of the corrugation and the other plies providing sufficient thermal insulation to allow the cup to be comfortably held.
Unfortunately cups using multi-ply corrugated paper material for their outer walls are relatively difficult to manufacture.